Platelets appears to play a significant role in the development and progression of coronary artery disease (CAD) and its complications. A prospective, double-blind, drug trial (HL23550) with dipyridamole and aspirin vs. placebo is being conducted in pts who have undergone a clinically indicated left ventriculogram and coronary arteriogram because of CAD. The primary endpoint to be compared in the treatment and placebo groups is the coronary arteriographic evidence of progression of CAD or development of new CAD.